In recent years, an organic light-emitting diodes (OLED) display has become a newly developed display device, and has been widely used in smart phones, televisions, mobile wearable devices, and micro-displays. This is because the OLED display has technical advantages of active light emission, a high response speed (1 μm), a wide color gamut, a high contrast, a low power consumption, a light weight, a thin thickness and good transparency, which perfectly satisfy the requirements of people in mobile Internet age on portability and flexible folding. Therefore, OLED is known as an excellent display technology to replace LCD.
The side-by-side pixilation of three primary colors of red (R), green (G), and blue (B) is the most mature technology among OLED full-color methods. In general, three types of sub-pixels of R, G, and B are alternately and repeatedly arranged in a plane, and three adjacent sub-pixels form a pixel unit which may emit any color, that is, a basic image unit. The pixel units are repeatedly arranged in the plane to form a display screen. The smaller size of the pixel indicates a higher resolution or the PPI (Pixels Per Inch) of the display, and a clearer displayed picture.
At present, in terms of device manufacture, vacuum evaporation is the most mature technology to form an OLED organic layer, in which small organic molecules are heated by an evaporation source, and are changed from an aggregation state to a gaseous state, to be deposited on a right above substrate. A fine metal mask (FMM) is attached to the underside of the substrate. The FMM has a pattern formed by a large number of meshes, such that in depositing sub-pixels of a color, other sub-pixels and non-coated regions between sub-pixels which do not require to be coated are sheltered, and only the sub-pixels required to be coated are coated. Nowadays, the resolution of the display device is required to be higher and higher, which requires the size of the pixel to be smaller and smaller. However, a PPI value of a conventional OLED which has a structure that sub-pixels R, G, and B are alternately and repeatedly arranged, has been close to a limit due to the limitation of the FMM manufacturing process and the coating process.
In order to overcome the limitation of the FMM manufacturing process, an existing pixel arrangement structure is to gather the sub-pixels of the same color together, so that two, three or four sub-pixels can be formed by evaporation through only one FMM hole. However, since a distance between sub-pixels becomes larger, the pixel arrangement structure has a serious disadvantage of graininess in monochrome displaying.
Another existing pixel arrangement structure is that a pixel is formed by sub-pixels of red (R) and green (G) or by sub-pixels of blue (B) and green (G), which achieves a high PPI by sharing sub-pixels of R and B. However, the pixel arrangement structure has a poor display effect for true colors.